Electronic pacemakers are used in children and adults with certain heart conditions that interfere with a normal heartbeat. However, these life-saving devices can't react the way the heart's own pacemaker normally does -- for example, raising the heart rate to help us climb stairs or react to a scary movie.
In the researchers' experiments, described in the Dec. 20 advance online edition of Circulation, human ES cells were genetically engineered to make a green protein, grown in the lab and then encouraged to become heart cells. The researchers then selected clusters of the cells that beat on their own accord, indicating the presence of pacemaking cells. These clusters triggered the unified beating of heart muscle cells taken from rats, and, when implanted into the hearts of guinea pigs, triggered regular beating of the heart itself.
"These implanted cells also responded appropriately to drugs used to slow or speed the heart rate, which electronic pacemakers can't do," says study leader Ronald Li, Ph.D., assistant professor of medicine. "But many challenges remain before this technique could be used for patients. We want to bring this to the clinic as fast as possible, but we need to be extremely careful. If this process isn't done properly, it could jeopardize a very promising field."
The genetic engineering of the ES cells, accomplished by Tian Xue, Ph.D., a postdoctoral fellow at the School of Medicine, inserted a gene (for green fluorescence protein) so that the human cells would be easily distinguished from animal cells in the experiments. Since the engineered cells survived and worked properly, other
Contact: Joanna Downer
Johns Hopkins Medical Institutions